1. Field of the Invention
This invention relates to radiation field analyzers.
2. Discussion of Prior Art
When a laser source illuminates a scene with coherent radiation the return field contains a significant amount of information about its three dimensional structure and the nature of its surface. The analysis of such fields provides an important basis for target search, tracking and non-cooperative identification procedures. Single aperture single detector heterodyne detection systems with fundamental mode local oscillators are only able to detect the fundamental mode component of the field returned from a scene with the result that a considerable amount of potentially useful information is lost. In the microwave domain this problem is overcome by using an array of sub-apertures. The radiation arriving at each sub-aperture is coherently detected with a separate local oscillator source and detector. In this manner the field across the array is measured in a piece-wise manner. Because of the much shorter wavelength of optical radiation and the different technologies involved, the implementation of sub-aperture receiver array concepts in the analysis of field returns from scenes illuminated with laser radiation has proved difficult in practice.